Band control system for a digital subscriber network and band control method therefor

ABSTRACT

A band control system of the present invention is applicable to a digital subscriber line network in which a first apparatus and a second apparatus situated at a subscriber station and a center, respectively, are interconnected by a metallic cable for interchanging at least a digital data signal with each other. The band control system includes a commanding device included in one of the first and said second apparatuses for monitoring the receipt of ATM (Asynchronous Transfer Mode) cells from the other apparatus and sending, based on the result of monitoring, a band variation command to the other apparatus to thereby cause it to vary a band by using a frequency band not used for signal transfer. A band varying device is included in the other apparatus for receiving the band variation command and varying the band in accordance with the command.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/046,241, filed Mar. 11, 2011, which is a continuation of U.S. patentapplication Ser. No. 11/754,059, filed May 25, 2007 (now U.S. Pat. No.7,929,454), which is a continuation of U.S. patent application Ser. No.10/173,813, filed Jun. 19, 2002 (now U.S. Pat. No. 7,239,647). Thecontents of all these applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a band control system for a digitalsubscriber network and a band control method therefor. Moreparticularly, the present invention relates to a band control systemimplementing flexible control and efficient use of a band between IADs(Integrated Access Devices) and a DSLAM (Digital Subscriber Line AccessMultiplexer) situated at subscriber stations and a center, respectively,and a control method therefor.

2. Description of the Background Art

A VoDSL (Voice over Digital Subscriber Line) network using an ATM(Asynchronous Transfer Mode) communication system and a DSL technologyprovides a transfer path for multimedia communication using voice, dataand image. DSL technologies implement high-speed digital transfer overmetallic cables, i.e., existing telephone subscriber lines.

A problem with the conventional DSL technologies is that the transferrate is dependent on the quality of metallic cables and transferdistance and therefore indefinite despite a preselected transfer rate.Consequently, a communication band statistically set beforehand bringsabout the congestion of ATM cells and thereby causes some users to beblocked. It is therefore necessary to dynamically control bandassignment in order to obviate the congestion of ATM cells.

Japanese Patent Laid-Open Publication No. 2000-184061, for example,discloses a technology for dynamically controlling band assignment in aDSL communication system. It has been customary with conventionaltechnologies, including the above technology, to send band controlinformation indicative of the variation of a communication band by usingspecial ATM cells, e.g., RM (Resource Management) cells. This, however,presses the communication band and thereby makes the use of thefrequency band uneconomical when such special ATM cells are used todynamically guarantee the band during communication.

Technologies relating to the present invention are also disclosed in,e.g., Japanese Patent Laid-Open Publication No. 11-331192.

SUMMARY OF THF INVENTION

It is an object of the present invention to provide a band controlsystem for a digital subscriber line network capable of solving theproblem stated above and a band control system therefor.

A band control system of the present invention is applicable to adigital subscriber line network in which a first apparatus and a secondapparatus situated at a subscriber station and a center, respectively,are interconnected by a metallic cable for interchanging at least adigital data signal with each other. The band control system includes acommanding device included in one of the first and said secondapparatuses for monitoring the receipt of ATM (Asynchronous TransferMode) cells from the other apparatus and sending, based on the result ofmonitoring, a band variation command to the other apparatus to therebycause it to vary a band by using a frequency band not used for signaltransfer. A band varying device is included in the other apparatus forreceiving the band variation command and varying the band in accordancewith the command.

A band control method for the band control system is also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription taken with the accompanying drawings in which:

FIG. 1 is a schematic block diagram showing a specific band controlsystem in accordance with the present invention;

FIG. 2 is a flowchart demonstrating the operation of the band controlsystem shown in FIG. 1;

FIG. 3 is a schematic block diagram showing specific configuration of aDSLAM included in a first embodiment of the present invention;

FIG. 4 shows a specific frequency characteristic of signals to beinterchanged between IADS shown in FIG. 1 and the DSLAM;

FIG. 5 is a schematic block diagram showing a specific configuration ofeach IAD;

FIG. 6 is a schematic block diagram showing a specific configuration ofa DSLAM included in a second embodiment of the present invention;

FIG. 7 is a schematic block diagram showing a specific configuration ofan IAD included in the second embodiment;

FIG. 8 is a flowchart demonstrating the operation of the secondembodiment;

FIG. 9 is a schematic block diagram showing a third embodiment of thepresent invention; and

FIG. 10 is a schematic block diagram showing a specific configuration ofan ATU-R (Asymmetric digital subscriber line Termination Units-Remote)included in the third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Briefly, in a VoDSL network that allows a plurality of digital voicesignals and a plurality of digital data signals to be interchanged viametallic wires, or existing telephone subscriber lines, by use of a DSLtechnology, the present invention provides a band control systemrealizing flexible control and efficient use of communication bandbetween IADs and a DSLAM situated at subscriber stations and a center,respectively, and a band control method therefor.

Further, the system and method of the present invention measure theamount of received ATM cells or the ratio of discarded ATM cells VC(Virtual Channel) by VC and then send a band variation command to anyone of the IADs by using a frequency band not used for signal transferin the VoDSL network, e.g., a frequency band lower than 4 kHz inclusive.This dynamically optimizes the frequency band for thereby promotingefficient operation of the VoDSL network.

Referring to FIG. 1 of the drawings, a specific configuration of a bandcontrol system in accordance with the present invention. As shown, theband control system includes a public switched telephone network 101, anIP (Internet Protocol) network 102, a voice GW (Gate Way) 103, a BAS(Broadband Access Server) 104, an ATM network 105, a DSLAM 106, IADs107, telephones 108, and personal computers or similar data terminals109. A band control method in accordance with the present invention isapplied to the DSLAM 106 and IADs 107. The telephones 108 and dataterminals 109 are assigned to voice telephone services and Internetaccess and other data communication services, respectively.

More specifically, the telephones 108-1 through 108-m (m being apositive integer) and data terminals 109-1 through 1-9-n (n being apositive integer) each are accommodated in one of the IADs 107-1 through107-x (x being a positive integer). The IADs 107 each are connected tothe DSLAM 106 by one of metallic cables 111-1 through 111-x. The voiceGW 103 is existing network equipment that repeats, when any one of thetelephones 108 effects a voice telephone service, all protocolsnecessary for connecting the ATM network 105 and switched telephonenetwork 101. Likewise, the BAS 104 is existing network equipment thatrepeats, when any one of the data terminals 109 effects an Internetaccess or similar data communication service, all protocols necessaryfor connecting the ATM network 105 and IP network 102.

FIG. 2 demonstrates the operation of the band control system inaccordance with the present invention. As shown, the DSLAM 106 measuresthe amount of ATM cells received from each IAD 107 or the ratio ofdiscarded ATM cells VC by VC (step S1). The DSLAM 106 then commands,based on the result of measurement, the IAD 107 to vary the frequencyband by using a frequency band not newly occupied by signal transfer ina VoDSL network, e.g., a frequency band lower than 4 kHz inclusive (stepS2). In response, the IAD 107 varies the frequency band of a VC newlydesignated by the DSLAM 106 (step S3).

As stated above, the band control system in accordance with the presentinvention sends band control information to the IAD 107 not by usingconventional special ATM cells, but by using a frequency band notoccupied by signal transfer. The system therefore solves the previouslystated problem particular to the conventional DSL communication system.It is therefore possible to dynamically maintain an optimalcommunication band between each IAD 107 and the DSLAM 106 for therebypromoting efficient use of the VoDSL network.

A first embodiment of the present invention also practicable with theconfiguration shown in FIG. 1 will be described hereinafter. Thedescription on the individual blocks shown in FIG. 1 will not berepeatedly made in order to avoid redundancy. The voice GW 103 has thepreviously stated function as existing network equipment. Morespecifically, the voice GW 103 communicates with the IADs 107 with asignaling procedure using, e.g., an LES (Lop emulation Service). Also,the voice GW 103 communicates with the switched telephone network 101with a signaling procedure using an FR-303 or similar time-divisioncommunication system.

The BAS 104 also has the function stated earlier as existing networkequipment. More specifically, the BAS 104 communicates with the ATMnetwork 105 with a signaling system using, e.g., a PPPoA (Point to PointProtocol over ATM) system. Also, the BAS 104 interchanges IP packetswith the IP network 101 by using an IP signaling system.

A specific configuration of the DSLAM 106 will be described withreference to FIG. 3. As shown, the DSLAM 106 includes an ATM networkinterface 201, an ATM cell multiplexer/demultiplexer 202, x (x being apositive integer) ATM cell queues 203 (203-1 through 203-x) and x centerDSL modems 204 (204-1 through 204-x) as conventional. In theillustrative embodiment, the DSLAM 106 additionally includes x bandcontrol information transmitters 205 (205-1 through 205-x) and x signalcouplers 206 (206-1 through 206-x).

Each band control information transmitter 205 measures, VC by VC, theamount of ATM cells received from the associated IAD 107 or the ratio ofdiscarded ATM cells. Assume that either the amount of received ATM cellsor the ratio of discarded ATM cells exceeds an allowable rangeimplementing preselected communication quality. Then, to command the IAD107 to vary the communication band assigned to the corresponding VC, thetransmitter 205 modulates a band control information signal to aconventional modem signal or similar signal that can be sent in afrequency band lower than 4 kHz inclusive. The modulated signal is fedto the associated signal coupler 206.

The signal coupler 206 couples a DSL signal received from the center DSLmodem 204 and the band control information signal received from the bandcontrol information transmitter 205 to thereby produce a signal, whichwill be described with reference to FIG. 4 later. This signal is sentfrom the signal coupler 206 to the IAD 107 connected to the DSLAM 106 bythe associated metallic cable 111. In addition, when the signal coupler206 receives a DSL signal from the IAD 107, the signal coupler 206simply transfers the DSL signal to the center DSL modem 203 without anyprocessing.

FIG. 4 shows specific frequency bands assigned to the signals to beinterchanged between each IAD 107 and DSLAM 106. As shown, the signalsconsist of a DSL signal or main information signal 121 and a bandcontrol information signal 122. A frequency band higher than 4 kHz and afrequency band lower than 4 kHz inclusive are assigned to the DSL signal121 and band control information signal 122, respectively, by way ofexample.

FIG. 5 shows a specific configuration of each IAD 107. As shown, the IAD107 includes a terminal DSL modem 302, an ATMcellularizer/decellularizer 304, a telephone interface 305, and a dataterminal interface 306 as conventional. In the illustrative embodiment,the IAD 107 additionally includes a signal uncoupler 301, and a bandcontrol information receiver 303.

The conventional telephone interface 305 allows various kinds oftelephone terminals 108 available for voice telephone services to beaccommodated in the IAD 107. For this purpose, the telephone interface305 functions to terminate POTS (Plain Old Telephone Service) interfacesassigned to traditional analog telephones and S/T point interfacesassigned to ISDN (Integrated Services Digital Network) terminaladapters.

Likewise, the conventional data terminal interface 306 allows variouskinds of data terminals 109 available for internet access and other datacommunication services to be accommodated in the IAD 107. For thispurpose, the data terminal interface 306 functions to terminate a USB(Universal Serial Bus), 10/100 Base-T or similar interface.

The signal uncoupler 301 separates the signals shown in FIG. 4 andreceived from the DSLAM 106 via the metallic cable 111 into the DSLsignal 121 and frequency control information signal 122 that lies in thefrequency band lower than 4 kHz inclusive. The DSL signal 121 and bandcontrol information signal 122 separated from each other are input tothe terminal DSL modem 302 and band control information receiver 303,respectively. On the other hand, when a DSL signal is input from theterminal DSL modem 302 to the signal uncoupler 301, the signal uncoupler301 simply transfers the DSL signal to the metallic cable 111 withoutany processing.

The band control information receiver 303 separates the band controlinformation sent from the DSLAM 106 from the band control informationsignal 122 and analyzes the information. The receiver 303 then causesthe ATM cellularizer/decellularizer 304 to vary the communication bandassigned to the corresponding VC directed toward the DSLAM 106.

Specific operations of the illustrative embodiment will be describedhereinafter. First, how signals flow when the telephone 108 accommodatedin any one of the IADs 107 communicates with the public switchedtelephone network 101 by using a voice telephone service will bedescribed.

Referring again to FIG. 1, as for the flow of signals from the telephonenetwork 101 toward the telephone 108, a digital voice signal based onthe time-division communication system is sent from the telephonenetwork 101 to the voice GM 103 and transformed to ATM cells thereby.The cellularized digital voice signal is sent from the voice GW 103 tothe DSLAM 106 via the ATM network 105. In the DSLAM 106, the ATM cellmultiplexer/demultiplexer 202 delivers the cellularized digital voicesignal to the center DSL modem 204 via one of the ATM cell queues 203corresponding to the IAD 107. The office DSL modem 204 modulates thecellularized digital voice signal to a DSL signal and sends the DSLsignal to the IAD 107 connected thereto by the metallic cable 111.

In the IAD 107 shown in FIG. 5, the terminal DSL modem 302 demodulatesthe DSL signal to thereby restore the original ATM cellularized voicesignal. Subsequently, the ATM cellularizer/decellularizer 304decellularizes the cellularized digital signal input from the terminalDSL modem 302. As a result, the decellularized digital voice signal isinput to the telephone interface 305. The telephone interface 305transforms the digital voice signal to a voice signal format matchingwith the telephone 108 and then sends the transformed voice signal tothe telephone 108.

The flow of signals from the telephone 108 toward the telephone network101 is identical with the flow described above except that the procedureis reversed in direction and will not be described specifically.

As stated above, the illustrative embodiment implements a bidirectionalvoice telephone service between the telephone 108 accommodated in theIAD 107 and the public switched telephone network 101.

Next, how signals flow when the data terminal 109 accommodated in anyone of the IADs 107 effects a data communication service with the IPnetwork 102 will be described hereinafter. Referring to FIG. 1, as forthe flow of signals from the IP network 102 toward the data terminal109, the IP network 102 sends an IP packet or an IP-packeted digitaldata signal to the BAS 104. The BAS 104 transforms the received IPpacket or the IP-packeted digital data to an ATM cell. TheATM-cellularized IP packet or the IP-packeted digital data signal issent to the DSLAM 106 via the ATM network 105. In the DSLAM 107, themultiplexer/demultiplexer 202, FIG. 3, delivers the ATM-cellularized IPpacket or the IP-packeted digital signal data to the center DSL modem204 via the ATM cell queue 203 corresponding to the IAD 107, whichaccommodates the data terminal 109. The center DSL modem 204 modulatesthe ATM-cellularized IP packet or the IP-packeted digital data signal toa DSL signal and sends the DSL signal to the IAD 107 via the metalliccable 111.

In the IAD 107, the terminal DSL modem 302, FIG. 5, demodulates the DSLsignal to thereby restore the ATM-cellularized IP packet or theIP-packeted digital data signal and feeds it to the ATMcellularizer/decellularizer 304. The ATM cellularizer/decellularizer 304decellularizes the ATM-cellularized IP packet or the IP-packeted digitaldata signal and inputs the resulting IP packet or the IP-packeteddigital data signal to the data terminal interface 306. The dataterminal interface 306 transforms the IP packet or the IP-packeteddigital data signal to a format matching with the data terminal 109 andthen sends the transformed IP packet or the transformed data signal tothe data terminal 109.

The flow of signals from the data terminal 109 toward the IP network 102is identical with the flow described above except that the procedure isreversed in direction and will not be described specifically.

As stated above, the illustrative embodiment implements a bidirectionaldata communication service between the data terminal 109 accommodated inthe IAD 107 and the IF network 102.

Hereinafter will be described a band control procedure to be executedbetween each IAD 107 and the DSLAM 106. When a plurality of voicetelephone services and a plurality of data communication services, bothof which are bidirectional, are effected at the same time, importanceshould be attached to the communication quality of voice telephoneservices. This is because voice telephone services allow information tobe interchanged between persons and therefore need real-timecommunication more than data communication services. It is thereforenecessary to reduce propagation delays as far as possible. In addition,voice quality falls with an increase in the number of ATM cellsdiscarded due to the failure of retransmission. On the other hand, datacommunication services should also be effected at high speed as possiblefor users' convenience.

In light of the above, in the illustrative embodiment, each band controlinformation transmitter 205, FIG. 3, measures the amount of ATM cellsreceived from the associated IAD 107 and present on the associated ATMcell queue 203 or the ratio of discarded ATM cells VC by VC (step S1,FIG. 2). Assume that the amount of ATM cells or the ratio of discardedATM cells exceeds an allowable range assigned to the communicationquality of a voice telephone service, which is determined by theprovider of the VoDSL network beforehand. Then, the band controlinformation transmitter 205 modulates the band control informationsignal 122, FIG. 4, to a conventional modem signal or similar signalthat can be sent in the frequency band lower than 4 kHz inclusive. Theband control information signal 122 is sent to the IAD 107 via thesignal coupler 206 in order to command the IAD 107 to vary the frequencyband of the VC on which the corresponding data communication service isheld (step S2, FIG. 2).

In the IAD 107 shown in FIG. 5, the band control information signal 122is routed through the signal uncoupler 301 to the band controlinformation receiver 303. The receiver 303 separates the band controlinformation signal 122 and analyzes the communication band designated bythe DSLAM 106. The receiver 303 then controls the ATMcellularizer/decellularizer 304 in order to narrow the communicationband assigned to the VC of the corresponding data communication serviceand directed toward the DSLAM 106 (step S3, FIG. 2).

On the other hand, assume that the amount of ATM cells or the ratio ofdiscarded ATM cells decreases below the allowable range assigned to thecommunication quality of the voice telephone service. Then, the DSLAM106 sends the band control information signal 122 to the IAD 107 in thepreviously stated manner. Again, the band control information receiver303 separates the band control information signal 122 and analyzes thecommunication band designated by the DSLAM 106. The receiver 303 thencontrols the ATM cellularizer/decellularizer 304 in order to broaden thecommunication band assigned to the VC of the corresponding datacommunication service and directed toward the DSLAM 106.

A second embodiment of the present invention will be describedhereinafter. The second embodiment is essentially similar to the firstembodiment except that the DSLAM 106 is also configured to vary thefrequency band of the VC designated by the IAD 107 for thereby furtherpromoting efficient operation of the VoDSL network.

As shown in FIG. 6 specifically, the DSLAM 106 includes signalcoupler/uncouplers 501 (501-1 through 501-x). Each signalcoupler/uncoupler 501 has, in addition to the function of the signalcoupler 206, FIG. 3, a function of separating the signal received fromthe IAD 107 into the DSL signal 121 and the signal 122 lying in thefrequency bend lower then 4 kHz inclusive and feeding the signal 122 toa band control signal transmitter/receiver 502.

The band control signal transmitter/receiver 502 has the followingfunction in addition to the function of the band control informationtransmitter 205, FIG. 3. The additional function is to separate the bandcontrol information signal sent from the IAD 107 from the signal 122input from the signal coupler/uncoupler 501, analyze the signal 122,control the ATM cell queue 203 in accordance with the result ofanalysis, and vary the communication band assigned to the correspondingVC and directed toward the IAD 107.

As shown in FIG. 7 specifically, the IAD 107 includes a signalcoupler/uncoupler 601 and a band control signal transmitter/receiver602. The signal coupler/uncoupler 601 has, in addition to the functionof the signal uncoupler 301, FIG. 5, a function of coupling the DSLsignal 121 received from the terminal DSL modem 302 and the band controlinformation signal 122 received from the band control informationtransmitter/receiver 602 and sending the resulting signal to the DSLAM106.

The band control information signal transmitter/receiver 602 has thefollowing function in addition to the function of the band controlinformation receiver 303, FIG. 5. The additional function is to measurethe amount of ATM cells received from the DSLAM 106 and input to the ATMcellularizer/decellularizer 304 or the ratio of discarded ATM cells VCby VC. When the amount of ATM cells or the ratio of discarded ATM cellsincreases above an allowable range assigned to communication quality,the band control information transmitter/receiver 602 modulates the bandcontrol information signal to a conventional modem signal or similarsignal that can be sent in the frequency band lower than 4 kHzinclusive. The modulated signal is sent to the signal coupler/uncoupler601 in order to command the signal coupler/uncoupler 601 to vary thecommunication band of the corresponding VC.

More specifically, as shown in FIG. 8, the IAD 107 measures the amountof ATM cells received from the DSLAM 106 or the ratio of discarded ATMcells VC by VC (step S11). The IAD 107 then commands the DSLAM 106 tovary the frequency band by using the band lower than 4 kHz inclusive(step S12). In response, the DSLAM 106 varies the frequency band of theVC designated by the IAD 107 (step S13).

As stated above, in the illustrative embodiment, the IAD 107 cancommand, based on the amount of ATM cells received from the DSLAM 106 orthe ratio of discarded ATM cells, the DSLAM 106 to vary thecommunication band VC by VC. It follows that the DSLAM 106 can narrow orbroaden the band of the VC designated by the IAD 107 accordingly.

A third embodiment of the present invention will be describedhereinafter. This embodiment is applicable to a DSL network configuredto promote high-speed Internet access and other data communicationservices by using metallic cables. A DSL network transforms only digitaldata signals to ATM cells and transfer the ATM cells via metalliccables. FIG. 9 shows a band control system representative of the thirdembodiment. As shown, the third embodiment includes x ATU-Rs 701 (701-1through 701-x) in place of the IADs 107-1 through 107-x, FIG. 1. The xATU-Rs 701 are connected to the DSLAM 106 by the metallic cables 111.

FIG. 10 shows a specific configuration of one of the ATU-Rs 701. Asshown, the ATU-R 701 includes the band control informationtransmitter/receiver 602 and signal coupler/uncoupler 601 in addition tothe conventional terminal DSL modem 302, ATM cellularizer/decellularizer304, and data terminal interface 306. How the illustrative embodimentexecutes bidirectional control over the communication band between theDSLAM 106 and each ATU-R 701 will be described hereinafter.

When the data terminal 109 accommodated in any one of the ATU-Rs effectsa data communication service with the IP network 102, signals flow inexactly the same manner as when the data terminal 109 accommodated inthe IAD 107 effects a data communication service with the IP network102.

First, a specific procedure for controlling the communication banddirected from the ATU-R 701 toward the DSLAM 106 when a plurality ofdata communication services are held will be described. In the DSLAM 106shown in FIG. 6, each band control information transmitter/receiver 502measures the amount of ATM cells received from the associated ATU-R 701and present on the associated ATM cell queue 203 or the ratio ofdiscarded ATM cells VC by VC (step S1, FIG. 2). Assume that the amountof ATM cells or the ratio of discarded. ATM cells increases above anallowable range assigned to the communication quality of a voicetelephone service, which is determined by the provider of the VoDSLnetwork beforehand. Then, the band control informationtransmitter/receiver 502 modulates the band control information signalto a conventional modem signal or similar signal that can be sent in thefrequency band lower than 4 kHz inclusive. The band control informationsignal is sent to the ATU-R 701 via the signal coupler/uncoupler 501 inorder to command the ATU-R 701 to vary the frequency band of the VC onwhich the data corresponding data communication service is held (stepS2, FIG. 2).

In the ATU-R 701 shown in FIG. 10, the band control information signalis routed through the signal coupler/uncoupler 601 to the band controlinformation transmitter/receiver 602. The transmitter/receiver 602analyzes the communication band designated by the DSLAM 106. Thetransmitter/receiver 602 then controls the ATMcellularizer/decellularizer 304 in order to narrow the communicationband assigned to the VC of the corresponding data communication serviceand for transmission to the DSLAM 106 (step S3, FIG. 2).

On the other hand, assume that the band control informationtransmitter/receiver 502 included in the DSLAM 106, FIG. 6, determinesthat the amount of ATM cells or the ratio of discarded ATM cells hasdecreased below the allowable range assigned to the communicationquality of the voice telephone service. Then, the DSLAM 106 sends theband control information signal to the ATU-R 701 in the previouslystated manner. Again, the band control information transmitter/receiver602 separates the band control information signal and analyzes thecommunication band designated by the DSLAM 106. The transmitter/receiver602 then controls the ATM cellularizer/decellularizer 304 in order tobroaden the communication band assigned to the VC of the correspondingdata communication service and adapted for transmission to the DSLAM106.

Next, a specific operation for controlling the communication banddirected from the DSLAM 106 toward any one of the ATU-Rs 701 will bedescribed. In the ATU-R 701 shown in FIG. 10, each band controlinformation transmitter/receiver 602 measures the amount of ATM cellsreceived from the DSLAM 106 and present in the ATMcellularizer/decellularizer 304 or the ratio of discarded ATM cells VCby VC (step S11, FIG. 8). Assume that the amount of ATM cells or theratio of discarded ATM cells increases above an allowable range assignedto the communication quality of a voice telephone service, which isdetermined by the provider of the VoDSL network beforehand. Then, theband control information transmitter/receiver 602 modulates the bandcontrol information signal to a conventional modem signal or similarsignal that can be sent in the frequency band lower than 4 kHzinclusive. The band control information signal is sent to the DSLAM 106via the signal coupler/uncoupler 601 in order to command the DSLAM 106to vary the frequency band of the VC on which the data correspondingdata communication service is held (step S12, FIG. 8).

In the DSLAM 106, the band control information signal is routed throughthe signal coupler/uncoupler 501 to the band control informationtransmitter/receiver 502. The transmitter/receiver 502 separates thecommunication band control signal and analyzes the communication banddesignated by the ATU-R 701. The transmitter/receiver 502 then controlsthe ATM cell queue 203 in order to narrow the communication bandassigned to the VC of the corresponding data communication service andadapted for transmission to the ATU-R 701 (step S13, FIG. 8).

On the other hand, assume that the band control informationtransmitter/receiver 602 included in the ATU-R 701 determines that theamount of ATM cells or the ratio of discarded ATM cells has decreasedbelow the allowable range assigned to the communication quality of thevoice telephone service. Then, the transmitter/receiver 602 sends theband control information signal to the DSLAM 106 in the previouslystated manner. Again, the band control information transmitter/receiver502 in the DSLAM 106 separates the band control information signal andanalyzes the communication band designated by the ATU-R 701. Thetransmitter/receiver 502 then controls the ATM cell queue 203 in orderto broaden the communication band assigned to the VC of thecorresponding data communication service and adapted for transmission tothe ATU-R 701.

As stated above, the illustrative embodiment provides high-quality datacommunication services by dynamically optimizing the frequency bandsbetween the DSLAM 106 and the ATU-Rs 701 in opposite directions, therebypromoting efficient operation of the DSL subscriber network.

In summary, it will be seen that the present invention obviatesuneconomical use of a communication band by preventing it from beingpressed. In addition, the present invention provides high-quality datacommunication services by dynamically optimizing frequency bands betweena DSLAM and IADs for thereby promoting efficient operation of a VoDSLnetwork.

Various modifications will become possible for those skilled in the artafter receiving the teachings of the present disclosure withoutdeparting from the scope thereof.

What is claimed is:
 1. A method comprising: measuring, by a device, oneof: an amount of data associated with received data from another device,or a ratio of discarded data associated with the received data, thereceived data being transmitted to the device using a particularfrequency band; transmitting, by the device and to the other device,information to cause the other device to adjust the particular frequencyband to an adjusted particular frequency band when the amount of data orthe ratio of discarded data exceeds a particular threshold, the adjustedparticular frequency band being different than the particular frequencyband; and receiving, by the device and after transmitting theinformation, additional data from the other device via the adjustedparticular frequency band.
 2. The method of claim 1, where the receiveddata corresponds to a Voice over Digital Subscriber Line (VoDSL)communication, and where the particular threshold relates to aparticular communication quality associated with the VoDSLcommunication.
 3. The method of claim 1, where transmitting theinformation includes: transmitting the information via a frequency bandthat is lower than the particular frequency band.
 4. The method of claim1, where the received data is received via a virtual channel associatedwith the other device.
 5. The method of claim 1, further comprising:measuring, for each respective virtual channel of a plurality of virtualchannels associated with one or more devices, one of: an amount of dataassociated with data received via the respective virtual channel using arespective frequency band, or a ratio of discarded data associated withthe data received via the respective virtual channel.
 6. The method ofclaim 5, further comprising: transmitting, to the one or more devices,information to adjust the respective frequency band, of one or morevirtual channels of the plurality of virtual channels, when the amountof data or the ratio of discarded data, measured for each virtualchannel of the one or more virtual channels, exceeds the particularthreshold.
 7. The method of claim 1, where the received data correspondsto a Voice over Digital Subscriber Line (VoDSL) communication, and wheretransmitting the information includes: transmitting the information viaa frequency band that is not used to transmit VoDSL communications.
 8. Asystem comprising: a device to: measure one of: an amount of dataassociated with received data from another device, or a ratio ofdiscarded data associated with the received data, the received databeing transmitted to the device using a particular frequency band; andtransmit, to the other device, information to cause the other device toadjust the particular frequency band to an adjusted particular frequencyband when the amount of data or the ratio of discarded data exceeds aparticular threshold, the adjusted particular frequency band beingdifferent than the particular frequency band.
 9. The system of claim 8,where the device is further to: receive additional data from the otherdevice via the adjusted particular frequency band.
 10. The system ofclaim 8, where, when transmitting the information, the device is to:transmit the information via a frequency band that is lower than theparticular frequency band.
 11. The system of claim 8, where the receiveddata is received via a virtual channel associated with the other device.12. The system of claim 8, where the device is further to: measure, foreach virtual channel of a plurality of virtual channels associated withone or more devices, one of: an amount of data associated with datareceived via the virtual channel using a respective frequency band, or aratio of discarded data associated with the data received via thevirtual channel.
 13. The system of claim 12, where the device is furtherto: transmit, to the one or more devices, information to adjust therespective frequency band, of one or more virtual channels of theplurality of virtual channels, when the amount of data or the ratio ofdiscarded data, measured for each virtual channel of the one or morevirtual channels, exceeds the particular threshold.
 14. The system ofclaim 8, where the received data corresponds to a voice communication,and where, when transmitting the information, the device is to: transmitthe information via a frequency band that is not used to transmit voicecommunications.
 15. A device comprising: a plurality of components to:determine whether one of: an amount of data, associated with receiveddata from another device, exceeds a particular threshold, or a ratio ofdiscarded data, associated with the received data, exceeds theparticular threshold, the received data being transmitted to the deviceusing a particular frequency band; and transmit, to the other device,information to cause the other device to adjust the particular frequencyband to an adjusted particular frequency band when the amount of dataexceeds the particular threshold or the ratio of discarded data exceedsthe particular threshold, the adjusted particular frequency band beingdifferent than the particular frequency band.
 16. The device of claim15, where the plurality of components are further to: receive additionaldata from the other device via the adjusted particular frequency band.17. The device of claim 15, where the received data corresponds to avoice communication, and where, when transmitting the information, theplurality of components are to: transmit the information via a frequencyband that is not used to transmit voice communications, the frequencyband being lower than the particular frequency band.
 18. The device ofclaim 15, where the device includes Digital Subscriber Line AccessMultiplexer (DSLAM), and the other device includes an Integrated AccessDevice.
 19. The device of claim 15, where the received data correspondsto a Voice over Digital Subscriber Line (VoDSL) communication, and wherethe particular threshold relates to a particular communication qualityassociated with the VoDSL communication.
 20. The device of claim 15,where the plurality of components are further to: measure, for eachvirtual channel of a plurality of virtual channels associated with oneor more devices, one of: an amount of data associated with data receivedvia the virtual channel using a respective frequency band, or a ratio ofdiscarded data associated with the data received via the virtualchannel; and transmit, to the one or more devices, information to adjustthe respective frequency band, of one or more virtual channels of theplurality of virtual channels, when the amount of data or the ratio ofdiscarded data, measured for each virtual channel of the one or morevirtual channels, exceeds the particular threshold.